1. Field of the Invention
The present invention relates, in general, to a method for forming fine patterns of a semiconductor device and, more particularly, to the use of dummy patterns, each having a size at which patterning is not permitted, to minimize the loss of pattern attributed to the proximity effect.
2. Description of the Prior Art
High integration of semiconductor devices requires many patterns of various sizes within a limited area. At an exposure process for forming desired patterns on a silicon substrate, a proximity effect, which is attributed to the refraction, scattering and/or interference of the light, usually occurs depending on the pattern density.
This effect results in a significant disadvantage in the formation of patterns. That is, the proximity effect may cause the light masks (or reticles) to be nonuniformly distorted, thereby causing the patterns to be dissected.
In order to better understand the background of the present invention, a description will be provided of the difference in proximity effect according to the difference in pattern density in a conventional method, with reference to some drawings.
FIGS. 1 and 2 show the conventional processes of pattern formation, illustrating the proximity effect generated by the pattern density of mask patterns.
First, FIG. 1A shows a layout 2 with a desired shape at such pattern density so as to minimize the proximity effect.
Subsequently, as shown in FIG. 1B, the layout 2 is used to give a reticle which is, in turn, used as a mask when exposing the pattern material on the silicon substrate 1 to light, to form a pattern 3. In this case, since the width of the patterns is almost the same as that of the layout 2, it is recognized that there is little alteration in the width attributed to the proximity effect.
In contrast, FIG. 2A shows a layout 11 with a line shape having such a pattern so as to show a large proximity effect.
Thereafter, as shown in FIG. 2B, a reticle is formed by use of the layout 11 and is then used as a mask to form a pattern 12 when the pattern material on the silicon substrate is exposed to light. In this case, the width of the pattern 12 is made thin by the proximity effect.
Since the pattern having such a pattern density induces a large proximity effect, as mentioned above, a serious photo bias is shown in the conventional process of pattern formation, and it is difficult to form a desired pattern. In addition, even at the pattern density which causes the proximity effect, etch bias is largely induced by a loading effect, so that the photo bias is disadvantageously required to be reduced during the exposure process.